Abstract—: A Cu2 –nSe phase has been prepared by self-propagating high-temperature synthesis in the combustion regime using mixtures of Cu and Se powders. We have carried out thermodynamic analysis of the formation of Cu2 –nSe from its constituent elements and calculated the adiabatic combustion temperature, which is 912 K for a mixture with the composition 2Cu + Se. Using X-ray diffraction data, we have determined the composition of the combustion product and the unit-cell parameters of the α- and β-phases of Cu2 –nSe in its homogeneity range. The phase composition of the material and the stoichiometry of Cu2 –nSe have been shown to depend on the composition of the starting mixture. Synthesis from 2Cu + Se and 1.85Cu + Se mixtures leads to predominant formation of the monoclinic phase α-Cu2 –nSe, whereas combustion of a 1.7Cu + Se mixture, having a considerable deviation from stoichiometry, yields the cubic phase β-Cu2 –nSe. The effect of isothermal annealing at 673 K on the phase composition of the material is examined.